Patent GB-1446403-A (GB)
Title: Scanning systems circuit block for an electronic watch
IPC: G06V10/10
Filed: 1974-09-13
Abstract: 1446403 Television MULLARD Ltd 13 Sept 1974 40068/74 Heading H4F A data scanning and storage system which may be used by partially sighted persons for producing an enlarged television image of printed data or in Optical Character Recognition systems, comprises: a hand held odometer including a rotor 6 which drives a stroboscopic electric pulse generator 9-12 at a rate dependent on the speed of the odometer; a line of 64 detectors 1 carried by the odometer; optical means 2-4 for imaging the data on to the detectors; a store for a two dimensional picture, Figs. 4 and 5, having elements arranged in rows R and columns S, the number of rows equalling the number of detectors; and input means for entering data brightness values into a column in response to a strobe pulse. In the preferred embodiment the store is of the two state binary type (on/off or black/white) from which data can be read out, non-destructively for use in a display device. The strobe pulses are produced by the stroboscopic effect of a pair of radially graduated discs 9, 10 one being fixed 10 and the other 9 coaxially driven by the rotor 6 via a friction gear train 7, 8 which allows a variety of drive ratios. The roller is housed in a scanning unit 20, Fig. 2A, which is rolled across a page of print P, Fig. 1. The print is illuminated by a lamp 5 in the unit 20 and projected through one lens 2, selected from turret 3, on to the detectors 1. The detectors 1 are self scanning and at any one time they emit a sequence of signals representing the brightness values of the data along one vertical line through the print, these signals are binary coded (black/white or on/off) in comparison with a threshold reference D.C. signal which may be varied by a potentiometer. As the head is moved over the page the strobe pulses are emitted, each of these pulses opens a gate and allows the next complete scanned output sequence from the detectors, to pass to the next column of store, the detector scan rate being faster than the envisaged strobe pulse frequency by a factor equal at least to the number of detectors. While no pulses emanate from the unit (i.e. when the roller is stationary relative thereto) the store content remains unchanged. Successive columns of the store may be considered as arranged in a circular fashion forming a cylinder Fig. 4(A) scanning by the unit being represented thereon by the input circuitry loading current data into column Me which contains the oldest stored data column immediately prior to accessing for input purposes and the newest stored data immediately after. Elemental scanning of the store for output purposes would not be fast enough for use in a scanned raster type display so a shift register 62, Fig. 5, is provided into which the elements of sub rows of data are simultaneously and non- destructively copied from the store prior to output in the form of a composite video signal used to modulate an appropriate low power V.H.F. or U.H.F. oscillator. Fig. 4A illustrates schematically the conceptual storage locations provided by 12 random access memory stores M0-M11 shown in Fig. 5. Each column L of picture information comprises 64 elements corresponding to the 64 photodetectors. The picture store is divided into 16 sectors S each containing 12 consecutive columns of the picture store. The sectors S correspond in number to the number 16 of columns in each of the 12 random access stores so that each sector S is built up from 12 columns taken one each from the 12 random access stores. Fig. 5 shows schematically the physical arrangement of the store and accessing circuit for output purposes. The shift register 62 contains 12 stages corresponding to the 12 random access stores. In Fig. 5 the 12 elements of row 26 in the fifth sector are being accessed simultaneously by the shift register prior to output. In addition to varying the magnification factor by changing either the gear ratio or the lens turret position, means are provided whereby the number of display lines on the scanned raster device corresponding to a given line of store, may be varied. The scanned raster device may be of the interlaced type.